Add deep search for filter taking in properties

[andershagbard]

This PR allows for backward compatibility deep search :woah:

Like so:

{{ input | where: 'some.nested.property', 'foo', deep: true }}
{{ input | where: 'some_nested_property', 'foo', deep: '_' }} # Custom separator

Added deep search for the following filters. This should be all Liquid filters which takes in a property argument:

• map
• sort
• sort_natural
• sum
• uniq
• where
• compact

[andershagbard]

@dylanahsmith I am not sure if you still work on Liquid, but I would love for someone in the Liquid team to take a look at this PR.

[andershagbard]

@karreiro @benjaminsehl ping

[karreiro]

👋 Hey @andershagbard,

Thank you for this PR. Could you please share your reasoning behind the deep parameter?

I feel like it was introduced with backward compatibility concerns; however, I believe it may bring a bit of complexity to the language and to language server implementations. I don't think it's required for backward compatibility, but I'm not sure if I'm missing something in that aspect.

Thanks again for this PR!

[andershagbard]

It's to safeguard against the JSON field type, which can contain dots in it's properties. It's an edge case I guess.

{
  "foo.bar": true
}

Ref: #1436 (comment)